Indicators: the red-cabbage rainbow

Tests: 6 of 11 right · Exam: 0 of 4 right · Kind: ★ · Understood: 9 of 15 · Run: 2026-10-18, commit f3c23ea72

Lesson 17 of the chemistry course of Mova's primary school, as Mova's small model took its tests: it had read this lesson and the ones before it and learned from their exercises. Each test shows the options in the order the student saw them, its choice, the right answer, the score of every option and why it chose. The lesson itself, sentence by sentence with trees and pragmatics: the lesson in the corpora.

Every question of this lesson and each of its options parsed by Mova, with trees and pragmatics: the lesson's questions in the corpora.

Test 1 · ★ · wrong ✗

Leo adds a mystery white powder dissolved in water to cabbage juice and it goes green. What does that tell him?

1. The powder is acidic — ← Mova's choice · no support
2. The powder is alkaline — ✓ the right answer · no support
3. The powder is neutral — no support
4. The cabbage has gone off — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 2 · ★ · wrong ✗

"my blueberry muffins came out GREEN wtf". What probably happened?

1. The oven was too cold — ← Mova's choice · no support
2. Too much baking soda in the batter — ✓ the right answer · no support
3. Green food colouring got in — no support
4. The berries had gone mouldy in the fridge — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 3 · ★ · right ✓

A spy cartoon shows lemon writing appearing by itself after an hour. What's the real way?

1. It shows only when warmed by a grown-up — ← Mova's choice · ✓ the right answer · score 7
2. It shows after an hour in the dark — no support
3. It shows when soaked in cold water — no support
4. It shows if you breathe on it — no support

Why: It took the question to ask what it is done to. It chose option 1 with score 7, the only option with support. Its support: lesson 17, line 17: «Lemon-juice writing is invisible until a grown-up warms the paper, when the juice turns brown before the paper does; spies once used invisible inks like this.», reached through the same lesson line as the sentence the question matched. What matched: the same action «warm» (+4); the same circumstance (+2); a different doer (counts against) (+1). · the question and its options parsed, with trees and pragmatics

Test 4 · ★ · wrong ✗

Zara drops red litmus into a cup of soapy water. What will she see?

1. It stays red — ← Mova's choice · no support
2. It turns blue — ✓ the right answer · no support
3. It turns yellow — no support
4. It turns black — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 5 · ★ · right ✓

If you dropped universal indicator into lemon juice and then into bleach, what would you see?

1. The cups would start fizzing — no support
2. No colour at all both times — score 2
3. Two very different colours — ← Mova's choice · ✓ the right answer · score 4
4. The same colour both times — score 2

Why: It took the question to ask what it is done to. It chose option 3 with score 4, against 2 for the next best. Its support: lesson 17, line 7: «The colour substance in red cabbage changes shape at different pH, and each shape has a different colour.», reached through the remembered sentence the question matched. What matched: it fills the role the question asks for (+3); the same property (+2); the same thing acted on «different colour» (+1). Against it: a different doer (counts against) (-2). · the question and its options parsed, with trees and pragmatics

Test 6 · ★ · wrong ✗

Mum says every coloured fruit and veg changes colour exactly like red cabbage. What's true?

1. Only fruit, never vegetables — no support
2. Only green vegetables change — no support
3. Yes, every plant colour is the same — ← Mova's choice · score 2
4. Not all: beetroot behaves differently — ✓ the right answer · no support

Why: It took the question to ask which statement is true. It chose option 3 with score 2, the only option with support. Its support: lesson 17, line 11: «Beetroot juice stays red in vinegar and turns more purple-brown in alkali; not every plant colour changes the same way.», reached through the option's own match among the sentences about the question's things. What matched: the same doer «plant colour» (+1); the same property (+1). The right option, 4, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 7 · ★ · right ✓

"the pool's making my eyes sting like mad". What could the test kit show?

1. There are too many swimmers — no support
2. The water is too cold — no support
3. The water is pure and neutral — no support
4. The water may be too acidic — ← Mova's choice · ✓ the right answer · score 4

Why: It took the question to ask which statement is true. It chose option 4 with score 4, the only option with support. Its support: lesson 17, line 16: «Pool test kits compare the colour of a water sample with drops added to a colour card; water that is too acidic stings the eyes.», reached through the same lesson line as the sentence the question matched. What matched: the same doer «water» (+2); the same property (+1); the same light verb (be, have, do, get, go) (+1). · the question and its options parsed, with trees and pragmatics

Test 8 · ★ · wrong ✗

Gran adds lemon to her black tea and it goes paler. Grandpa says it's because lemon is yellow. What's true?

1. The lemon cools the tea down — ← Mova's choice · score 6
2. Lemon soaks up the tea leaves — no support
3. Yellow lemon juice mixes with brown tea — no support
4. Acid changes the colours in the tea — ✓ the right answer · no support

Why: It took the question to ask which statement is true. It chose option 1 with score 6, the only option with support. Its support: lesson 17, line 4: «Indicators hide in everyday life: lemon makes tea paler, a curry stain turns red when washed with soap, and pool keepers check the water every day with drops a…», reached through the remembered sentence the question matched. What matched: the same doer «lemon» (+4); the same thing acted on «tea» (+4). Against it: a different action (counts against) (-2). The right option, 4, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 9 · ★ · right ✓

Which would turn red cabbage juice pink?

1. Baking soda — no support
2. Soap — no support
3. Vinegar — ← Mova's choice · ✓ the right answer · score 4
4. Plain water — no support

Why: It took the question to ask who or what does it. It chose option 3 with score 4, the only option with support. Its support: lesson 17, line 1: «Chop red cabbage, soak it in hot water, and you get a purple juice. Add a splash of vinegar and it turns pink; add a pinch of baking soda and it turns blue-gre…», reached through the same lesson line as the sentence the question matched. What matched: it fills the role the question asks for (+3); the same doer «vinegar» (+2). Against it: a different action (counts against) (-1). · the question and its options parsed, with trees and pragmatics

Test 10 · ★ · right ✓

"my white shirt had curry on it and now the stain's gone RED after washing??" Why?

1. The washing machine added its own red dye — no support
2. Turmeric turns red with alkaline soap — ← Mova's choice · ✓ the right answer · score 4
3. The curry was secretly tomato — no support
4. Hot water burns stains red — no support

Why: It took the question to ask which statement is true. It chose option 2 with score 4, the only option with support. Its support: lesson 17, line 4: «Indicators hide in everyday life: lemon makes tea paler, a curry stain turns red when washed with soap, and pool keepers check the water every day with drops a…», reached through the remembered sentence the question matched. What matched: the same action «turn» (+4); the same property (+2). Against it: a different doer (counts against) (-2). · the question and its options parsed, with trees and pragmatics

Test 11 · ★ · right ✓

If a lab had no indicators at all, how could a scientist still measure pH?

1. By tasting every liquid — no support
2. By looking at it under a lamp — no support
3. With an electronic pH meter — ← Mova's choice · ✓ the right answer · score 6
4. By weighing the liquid — no support

Why: It took the question to ask what something is like. It chose option 3 with score 6, the only option with support. Its support: lesson 16, line 4: «Scientists measure acids and alkalis on the pH scale from 0 to 14: below 7 is acid, 7 is neutral like pure water, above 7 is alkali. Strong alkalis, like oven…», reached through the remembered sentence the question matched. What matched: the same action «measure» (+4); the same doer «scientists» (+4). Against it: a different thing acted on (counts against) (-2). · the question and its options parsed, with trees and pragmatics

Exam question 1 · formal language · wrong ✗

Identify the term designating a substance whose colour reveals whether a solution is acidic or alkaline.

1. A catalyst — ← Mova's choice · no support
2. A solvent — no support
3. An indicator — ✓ the right answer · no support
4. A neutraliser — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Exam question 2 · formal language · wrong ✗

It is given that red cabbage juice is added to a solution of baking soda. Determine the colour most likely to be observed.

1. Pink-red — ← Mova's choice · no support
2. Deep black — no support
3. Colourless — no support
4. Blue-green — ✓ the right answer · no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Exam question 3 · formal language · wrong ✗

Which of the following statements most accurately characterises universal indicator?

1. It is a single dye derived exclusively from red cabbage — ← Mova's choice · score 9
2. It is a mixture of indicators producing a distinct colour for each pH — ✓ the right answer · score 7
3. It is a device that measures pH by electricity — score 7
4. It changes colour only in the presence of strong acids — score 7

Why: It took the question to ask who or what does it. It chose option 1 with score 9, against 7 for the next best. Its support: lesson 17, line 3: «Scientists use indicators too: litmus paper, made from lichens, turns red in acid and blue in alkali. Universal indicator mixes several dyes, so each pH gets i…», reached through a sentence linked to the one the question matched. What matched: it fills the role the question asks for (+4); the same doer «universal indicator» (+3); the same thing acted on «several dyes» (+2). The right option, 2, scored 7. · the question and its options parsed, with trees and pragmatics

Exam question 4 · formal language · wrong ✗

Select the response consistent with the established facts concerning litmus.

1. It turns blue in acid and red in alkali, and its dye is obtained from cabbage — ← Mova's choice · no support
2. It turns red in acid and blue in alkali, and its dye is obtained from lichens — ✓ the right answer · no support
3. It remains unchanged in acid and turns green in alkali — no support
4. It is a recent invention of the present century — no support

Why: Nothing it remembers matched the question, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

This page in Markdown → https://md.mova.elamur.ai/free/en/school-run/chemistry/17-indicators-the-red-cabbage-rainbow/